Hamas said - and to a certain extent justifiably - that Israel had exceeded the unwritten rules of the game. The Qassam had been fired by a marginal Palestinian group, and the accepted response would have been a bombing of empty Hamas offices or an escape tunnel without casualties.

If I get it right, Hamas underlings, obedient or not, are allowed to shoot at civilians sincerely hoping and probably praying to finally get a big hit while Israel is supposed to not harm Hamas fighters, let alone civilians.

An example of skewed reporting, as if another were needed. The lead story at Google news announces the Israeli shelling has killed two Palestinian teenagers. http://www.monstersandcritics.com/news/middleeast/news/article_1627443.php/Israeli-shelling-kills-two-Palestinian-teenagers-in-Gaza

Jerusalem Post reports:

On Saturday night, IDF tanks opened fire at two Palestinians who were moving suspiciously in an area that is off limits to Palestinians near the border. Medical officials in Gaza said that two known terrorists were killed.

This appears towards the end of a story on an attack on an Israeli tank. http://www.jpost.com/Defense/Article.aspx?id=213012